Addressing, command protocol, and electrical interface for non-volatile memories utilized in recording usage counts sensor

ABSTRACT

Electrical interfaces, addressing schemes, and command protocols allow for communications with memory modules in computing devices such as imaging and printing devices. Memory modules may be assigned an address through a set of discrete voltages. One, multiple, or all of the memory modules may be addressed with a single command, which may be an increment counter command, a write command, a punch out bit field, or a cryptographic command. The commands may be transmitted using a broadcast scheme or a split transaction scheme. The status of the memory modules may be determined by sampling a single signal that may be at a low, high, or intermediate voltage level.

Pursuant to 37 C.F.R. §1.78, this application is a continuation andclaims the benefit of the earlier filing date of application Ser. No.11/406,542, filed Apr. 19, 2006, entitled “Addressing, Command Protocol,and Electrical Interface for Non-Volatile Memories Utilized in RecordingUsage Counts,” the content of which is hereby incorporated by referenceas if fully set forth herein.

In addition, this present application is related to U.S. applicationSer. No. 11/154,117, filed Jun. 16, 2005, which is hereby incorporatedby reference herein as if fully set forth herein.

FIELD OF THE INVENTION

The present invention relates generally to non-volatile memories, andmore specifically, to addressing schemes, command protocols, andelectrical interfaces for non-volatile memories utilized in recordingthe usage of a device.

BACKGROUND OF THE INVENTION

Non-volatile memory modules are commonly found in computing devices forrecording the usage of components, including consumable componentshaving a limited life span. For instance, non-volatile memory modulesare common in imaging and printing devices, such as in multifunctionprinters, for recording the use of components such as fusers,accumulation belts, and the like, and for recording the use ofconsumables such as print cartridges. In imaging or printing devices,for instance, usage may be recorded based upon the number of pagesprinted by the device, or based upon the partial or full depletion ofthe print cartridges. Such usage counts are helpful in a variety ofways, including for billing purposes and in monitoring the status and/oruse of consumable components.

As computing devices have advanced and become more complex, the numberof non-volatile memory modules included within each device hasincreased. The speed with which each non-volatile memory module must beupdated or read in a computing device has also increased. Continuingwith the illustrative example of printing and imaging devices, the speedand page rates of these devices are constantly improving. Therefore, notonly do the contents of a greater number of non-volatile memory moduleshave to be updated, but the contents of these memory modules must beupdated in a shorter amount of time to keep up with the faster pagerates. In imaging and printing devices, because conventional many memorymodules have relatively long wait times for updating, faster page ratespresent difficulties in updating each of the non-volatile memories in adevice in a timely manner.

In addition, non-volatile memory modules (e.g., EEPROM, NOR flashmemory, NAND flash memory, etc.) in computing devices may experiencedegradation during operation, thereby necessitating error handling tomitigate interruption of operation of the memory modules. Further,non-volatile memory modules may be physically part of removeable and/orconsumable components of a computing device, such as printer cartridges.Because such removeable and/or consumable components should be easilyinstalled and removed by users, there is a cost premium associated witheach electrical connection between the computing device and it'sremoveable and/or consumable component, as exists, for instance, with aprinting device and a printer cartridge. By utilizing multi-level oranalog level communication techniques appropriately, the number of theseelectrical connections can be minimized, thereby helping to increasereliability and decrease cost.

Conventional protocols do not sufficiently handle all of these problemsdiscussed. Thus, there remains an unsatisfied need in the industry foraddressing schemes, command protocols, and electrical interfaces forquickly updating non-volatile memories, such as in non-volatile memorymodules utilized in imaging and printing devices.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding addressing schemes, command protocols, and electricalinterfaces that quickly update memory modules, such as non-volatilememory modules, in computing devices such as imaging and printingdevices.

According to an embodiment of the present invention, there is a methodof updating memory modules. The method includes receiving, at a firstmemory module, a first command transmitted from a processing device,transmitting, from the first memory module to a processing device, afirst indication that the first command was received without error,receiving at a second memory module, a second command transmitted fromthe processing device, wherein the processing device transmits thesecond command responsive to receiving the first indication transmittedfrom the first memory module, and transmitting, from the second memorymodule to the processing device, a second indication that the commandwas received without error, where the first and second processingmodules process the respective first and second commands, at least inpart, concurrently.

According to an aspect of the invention, the second memory modulereceiving the second command transmitted from the memory module mayoccur concurrently, at least in part, with the first memory moduleprocessing the first command. In addition, the second memory moduletransmitting the second indication to the processing device may occurconcurrently, at least in part, with the first memory module processingthe first command. According to another aspect of the invention, a timeassociated with the first memory module processing the first command maybe greater than a time associated with the first memory module receivingthe first command and transmitting the first indication. A timeassociated with the first memory module processing the first command maybe substantially the same as a time associated with the second memorymodule processing the second command. Likewise, a time associated withthe first memory module receiving the first command and transmitting thefirst indication may be substantially the same as a time associated withthe second memory module receiving the second command and transmittingthe second indication.

In accordance with another aspect of the invention, the first commandand the second command are substantially the same. The first command andthe second command may be associated with updating contents of therespective first and second memory modules. The first and secondcommands may include an increment counter command operable to instructthe respect first memory module and second memory module to increment acounter. According to another aspect of the invention, the first andsecond commands may each comprise a command associated with one or morecryptographic operations such as encryption or decryption.

According to another embodiment of the present invention, there is amethod of communicating with memory modules. The method includesdetermining, at a processing device, that the first and second memorymodules are ready to receive data, generating, at the processing device,a first packet comprising a first command and a first memory moduleaddress associated with the first memory module, transmitting the firstpacket from the processing device to the first memory module, receiving,at the processing device, a first confirmation signal from the firstmemory module, the first confirmation signal indicating that the firstmemory module received the first command without error, and in responseto receiving the first confirmation signal, generating, at theprocessing device, a second packet comprising a second command and asecond memory module address associated with the second memory module.The method further includes transmitting the second packet from theprocessing device to the second memory module, and receiving, at theprocessing device, a second confirmation signal from the second memorymodule, the second confirmation signal indicating that the second memorymodule received the second command without error, where the first andsecond memory modules process at least a portion of the respective firstand second commands concurrently.

According to an aspect of the present invention, the second command issubstantially the same as the first command. The first and secondcommands may each comprise one or both of a decryption command and aencryption command. According to another aspect of the invention, atleast a portion of a time associated with the processing devicetransmitting the second packet and receiving the second confirmationsignal may occur concurrently with a time associated with the firstmemory module processing the first command. The time associated with thefirst memory module processing the first command may be substantiallylarger than a time associated with the processing device transmittingthe second packet and receiving the second confirmation signal.

According to yet another embodiment of the present invention, there is amethod of updating memory modules. The method includes during a firsttime period, a first memory module receiving a first command from aprocessing device and transmitting a first signal to the processingdevice, the first signal indicating a successful reception of the firstcommand, during a second time period immediately following the firsttime period, the first memory module processing the first command, wherethe second time period is substantially greater than the first timeperiod, during a third time period immediately following the first timeperiod and overlapping at least in part with a beginning of the secondtime period, a second memory module receiving a second command from theprocessing device and transmitting the second signal to the processingdevice, the second signal indicating a successful reception of thesecond command, and during a fourth time period immediately followingthe third time period and overlapping the second time period, the secondmemory module processing the second command.

According to an aspect of the present invention, the first and secondcommands are substantially the same, thereby making the lengths of thesecond time period and fourth time periods substantially the same. Thelengths of the first and third time periods may also be substantiallythe same. The lengths of the second and fourth time periods may besubstantially larger than the lengths of the first and third timeperiods. According to another aspect of the invention, each of the firstand second commands may be associated with write commands andcryptographic commands.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1A is a schematic of an illustrative electrical interface,according to an embodiment of the present invention.

FIG. 1B is a schematic of an alternative manner by which the electricalinterface of FIG. 1A may be achieved by an electronic assembly includingintegrated circuits, according to an illustrative embodiment of thepresent invention.

FIG. 1C is a schematic of an illustrative electrical interface,according to an embodiment of the present invention.

FIGS. 2A and 2B are illustrative memory module addresses according to anembodiment of the present invention.

FIG. 3 is a block diagram flow chart of a write data operation,according to an illustrative embodiment of the present invention

FIGS. 4A and 4B are illustrative command protocols, according to anembodiment of the present invention.

FIG. 5 is a block diagram flow chart of a read data operation, accordingto an illustrative embodiment of the present invention.

FIGS. 6A and 6B are illustrative command protocols, according to anembodiment of the present invention.

FIG. 7 shows a block diagram flow chart illustrating a method ofcommunicating with one or more memory modules, according to oneembodiment of the present invention.

FIG. 8A is a time-flow diagram for a broadcast scheme, according to anembodiment of the present invention.

FIG. 8B is a time-flow diagram for a split transaction scheme, accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present inventions now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

Further, although the present invention is described in the context ofaddressing schemes, command protocols, and electrical interfaces forquickly updating non-volatile memories in imaging and printing devices,it will be appreciated that the present invention may be implemented inany device having non-volatile memories. This may include mobile phones,handheld computers, laptop computers, personal computers, servers,mainframe computers, personal digital assistants, and the like, anddevices having minimal processing power and functionality, such as indevices with dedicated circuits for performing preprogrammed oruncomplicated tasks. In brief, the present invention may be implementedin any computing device in which the usage of components may wish to berecorded using non-volatile memory. Therefore, the embodiments hereindescribing non-volatile memories for tallying page counts and recordingthe depletion of ink in ink or toner cartridges are for illustrativepurposes only and are not intended to be limiting examples.

In imaging and printing devices, page counts recorded by non-volatilememory modules (“memory modules”) may be incremented as pages areprinted. Page counts may include the total number of pages printed by aprinter and the total number of pages printed for each of a number ofprint categories. Recording the number of pages for individual printcategories permits the recording of page counts for specific types ofprinting tasks, such as the total number of color pages, monochromepages, letter size pages, legal size pages, transparencies, etc., thatmay be printed. In addition to recording page counts, non-volatilememory modules may be packaged with reservoirs such as ink or tonercartridges, and the memory modules may contain one or more bit fieldsfor recording the depletion of the reservoirs. By comparison, each bitfield may be in either an erased or programmed state (e.g., a “0” or“1”) while each page count may include a plurality of bits representinga numeric value. As an example, a non-volatile memory module providedwith a toner cartridge may contain thirty-two bit fields, and as aparticular amount of toner has been depleted (e.g., 1/32 of the totaltoner), a bit field may be “punched out,” thereby changing the bit fieldfrom an erased state to a programmed state. For instance, the value inthe bit field may be changed from an initial value of “0” to a value of“1”. In this illustrative example, all thirty-two bit fields may bepunched out after all of the toner had been depleted, thereby signifyingfull depletion of the toner cartridge. It will be appreciated by one ofordinary skill in the art that imaging and printing devices may containnon-volatile memory modules that have one or more counts, resource bitfields, or a combination thereof.

Embodiments of the present invention describe electrical interfaces,addressing schemes, and command protocols for efficiently commanding asingle memory module, a group of memory modules, or all of the memorymodules in an imaging or printing device. According to one aspect of theinvention, each memory module in the imaging or printing device may bedirected to increment one or more page counts by a specified value or topunch out a resource bit field. In order to direct a group of memorymodules with a common command, the group of memory modules may besynchronized prior to issuance of the command. Further, memory modulesmay be able to report errors and obtain assistance in resolving thoseerrors from a processing device. A given count or resource bit field ina non-volatile memory module may degrade with use, and therefore it maybe necessary to adjust the location of the count or bit field.

I. Electrical Interface

FIG. 1A illustrates an electrical interface 100 according to anillustrative embodiment of the present invention. The interface 100includes a processing device 101 in communication with a plurality ofnon-volatile memory modules 103 a, 103 b, . . . 103 x, which may containone or more counts, bit fields, or a combination thereof. According toone aspect of the invention, the processing device 101 may be anapplication-specific integrated circuit (ASIC). According to anotheraspect of the invention, the processing device 101 may be a generalprocessor or microprocessor running on a computing device to execute thefunctions described herein. To implement the functions described herein,the processing device 101 may also include software, hardware, or acombination thereof, and may include one or more integrated componentsin close proximity or components that are distributed throughout animaging and printing device.

As shown in FIG. 1A, the processing device 101 controls a voltageregulator 102 that provides a voltage source 104 to the memory modules103 a, 103 b, . . . 103 x. According to a preferred embodiment, thevoltage source for the memory modules 103 a, 103 b, . . . 103 x may be acommon voltage source. The memory modules 103 a, 103 b, . . . 103 x inthe illustrative electrical interface 100 operate at 3.3V, but it willbe appreciated by one of ordinary skill in the art that non-volatilememory modules such as the memory modules 103 a, 103 b, . . . 103 xshown in FIG. 1 may operate at other voltages. As illustrated in FIG.1A, the non-volatile memory modules 103 a, 103 b, . . . 103 x are alsoprovided with a common ground reference 106.

The processing device 101 may exchange data with one or more of thenon-volatile memory modules 103 a, 103 b, . . . 103 x through anaddress/data channel 108. According to one embodiment of the presentinvention, the address/data channel 108 may include a unidirectionalfirst channel and a unidirectional second channel. In particular, datafrom the processing device 101 may be sent over the first channel to thememory modules 103 a, 103 b, . . . 103 x using an asynchronousmodulation technique and a transmission rate supported by the memorymodules 103 a, 103 b, . . . 103 x. Similarly, data may be sent from thememory modules 103 a, 103 b, . . . 103 x to the processing device 101over the second channel utilizing an asynchronous modulation techniqueand a transmission rate supported by the memory modules 103 a, 103 b, .. . 103 x. According to one aspect of the invention, the transmissionrate may be common to all of the memory modules 103 a, 103 b, . . . 103x. In a preferred embodiment, the transmission rates for both the firstand second channels may be between approximately 38,400 bits/second and115,200 bits/second, though the transmission rates may vary depending onthe specific types of memory modules utilized. It will be appreciatedthat other transmission rates may also be used, including those notsupported by all of the memory modules 103 a, 103 b, . . . 103 x. Forexample, one memory module may transmit a response to a read command ata faster rate than another memory module.

According to other embodiments of the present invention, theaddress/data channel 108 may only include a single bidirectional channelcapable of sending and receiving data between the processing device 101and the memory modules 103 a, 103 b, . . . 103 x. A singlebi-directional address/data channel 108 may use an asynchronousmodulation technique and a transmission rate supported by the memorymodules 103 a, 103 b, . . . 103 x. When a single bi-directional channelis used, the processing device 101 may wait before current commands inprocess are completed before issuing additional commands to the memorymodules 103 a, 103 b, . . . 103 x. In addition, it will be appreciatedthat any command requiring a response from a memory module 103 a, 103 b,. . . 103 x may be issued over the address/data channel 108 to a singlememory module 103 a, 103 b, . . . 103 x at a time. To prevent othermemory modules from utilizing the address/data channel 108 while anothermemory module is transmitting data, a half-duplex sharing technique orother scheduling method may be implemented. Furthermore, it will beappreciated by those of ordinary skill in the art that otheralternatives for the address/data channel 108 may be possible to executethe processing device's 101 exchange data with one or more of thenon-volatile memory modules 103 a, 103 b, . . . 103 x, such as the useof two bi-directional channels, and that other transmission techniquesknown to those of ordinary skill in the art may be used to effectcommunication via the address/data channel 108.

As illustrated in FIG. 1A, the processing device 101 receives the statusof the memory modules 103 a, 103 b, . . . 103 x through a status channel110. According to one embodiment of the present invention, the statuschannel 110 may include a first channel representing a busy/availablestatus and a second channel representing an error/no-error status. In apreferred embodiment, the busy/available status may be provided on thefirst channel by effectively “anding” the busy/available output signalsfrom each of the memory modules through the use of anopen-collector/open-drain 112. The open-collector/open-drain 112 mayinclude one or more common resistors and one or more capacitors. In sucha configuration, each memory module 103 a, 103 b, . . . 103 x may outputa high voltage signal if it is able to accept a command, or a lowvoltage signal if it is busy executing a command. Thus, if all of thememory modules 103 a, 103 b, . . . 103 x are available, then the firstchannel signal may be pulled up to a “high” voltage by the resistor inthe open-collector/open-drain 112, signifying that all of the memorymodules 103 a, 103 b, . . . 103 x are available.

On the other hand, if any memory module 103 a, 103 b, . . . 103 x isbusy, then the first channel signal may be pulled to a “low” voltageclose to ground by the open-collector/open-drain 112. If at least onememory module 103 a, 103 b, . . . 103 x is busy, the processing device101 may wait until the first channel signal is pulled to a high voltagelevel before issuing a subsequent command to the memory modules 103 a,103 b, . . . 103 x. In this manner, the processing device 101 maysynchronize the memory modules 103 a, 103 b, . . . 103 x before issuinga common command, such as an increment counter command, to a pluralityof the memory modules 103 a, 103 b, . . . 103 x. Similarly, the secondchannel may also effectively “and” the error/no-error output signalsfrom each of the memory modules. This may also be provided with anotheropen-collector/open-drain 112 having a common resistor and capacitor.

Each of the memory modules 103 a, 103 b, . . . 103 x may output a highvoltage signal on the second channel when there is no error detected anda low voltage signal if an error is detected. Thus, if one of the memorymodules 103 a, 103 b, . . . 103 x has an error, the second channel maybe pulled to a low voltage by the open-collector/open-drain 112,signifying that at least one memory module 103 a, 103 b, . . . 103 xcontains an error. If all of the memory modules 103 a, 103 b, . . . 103x are error-free, then the second channel may be pulled to a highvoltage. All of the memory modules 103 a, 103 b, . . . 103 x will beready and error-free if the first and second channels are at a highvoltage level. It will be appreciated by one of ordinary skill thatthere are many alternatives to the “anding” function ofopen-collector/open drain 112 discussed above. For example, a pluralityof physical “and” gates can be used instead of theopen-collector/open-drain 112.

According to another embodiment of the present invention, the statuschannel 110 may include only a single channel capable of representingthe ready, error, and busy states for the memory modules 103 a, 103 b, .. . 103 x. When only a single channel is used, all addressed memorymodules 103 a, 103 b, . . . 103 x may release their respective busysignals from a low voltage level to a high voltage level after eachfinishes processing its current command. The status channel 110 may thenbe pulled to a high voltage level by the open-drain/open-collector 112.Once the addressed memory modules 103 a, 103 b, . . . 103 x havecompleted their commands and released each of their output signals abovethe low voltage, any memory module that needs to report an error mayhold the status channel 110 at an intermediate voltage level that ishigher than the low voltage level (e.g., close to ground) but lower thanthe high voltage (e.g., approximately 3.3V). For instance, each of thememory modules 103 a, 103 b, . . . 103 x may use a 1.5V zener diodecomponent to ground to provide the intermediate voltage level. Othermethods of providing an intermediate voltage levels level mayalternatively be implementing implemented using resistors, as is knownin the art, such as using a 5.1K Ωresistance to ground to provide theintermediate voltage level. In this way, a single status channel 110 maybe sufficient for reporting the ready, error, and busy states of thememory modules 103 a, 103 b, . . . 103 x thereby reducing the electricalconnections required between the processing device 101 and the memorymodules 103 a, 103 b, . . . 103 x.

It will be appreciated by one of ordinary skill in the art that the low,high, and intermediate voltage levels do not have to correspond to thebusy, error, and ready status, respectively, of the memory modules 103a, 103 b, . . . 103 x. According to an alternative embodiment, the lowvoltage level may correspond to a ready status while a high voltagelevel may correspond to a busy level. According to another embodiment,the address/data channel 108 may be utilized to transmit the status ofone or more of the memory modules 103 a, 103 b, . . . 103 x to theprocessing device 101. For example, the processing device may wait toreceive a ready status from each of the memory modules 103 a, 103 b, . .. 103 x on the address/data channel 108 before issuing a subsequentcommand.

As illustrated in FIG. 1A, the controlling computer system 101 may alsoprovide a common time reference to the memory modules 103 a, 103 b, . .. 103 x through a clock channel 121. According to one embodiment of thepresent invention, the clock channel 121 may operate at a frequencydirectly correlated to the bit rate of the Address/Data channel 108 ormay operate at a frequency unrelated to this bit rate. Phase-locked-loopcircuits present in each memory module 103 a, 103 b, . . . 103 x may usethe common time reference provided by the clock channel 121. It will beappreciated by one of ordinary skill in the art that the clock channel121 may either be a fixed frequency or a modulated frequency to spreadthe electromagnetic emissions associated with the clock channel 121 overa wider frequency range.

FIG. 1B is a schematic showing an alternative manner by which the memorymodules 103 a, 103 b, . . . 103 x in the illustrative electricalinterface of FIG. lA may be achieved via an electronic assembly 162including several integrated circuits, according to an illustrativeembodiment of the present invention. More specifically, in FIG. 1B anelectronic assembly 162 includes a memory module 150 that includes aPower-On Reset Detector Integrated Circuit (IC) 156, a Secure Memory IC152, and an Analog-to-Digital (A/D) Converter IC 154. Each of the ICs152, 154, 156 act in concert to implement the memory modules 150described above with respect to FIG. 1. Thus, the memory module 150implemented by a single electronic assembly 162 of FIG. 1B is equivalentto the multiple memory modules 103 a, 103 b, . . . 103 x discussed abovewith respect to FIG. 1A. To enable a single electrical connection to thememory module 150 to carry complete memory module 150 status (i.e.,ready/busy/error) information, FIG. 1B illustrates the use ofconventional open collector output circuits 159, 161 from the securememory IC 152 and a zener diode 158. Other arrangements for carryingstatus information, including those described above with respect to FIG.1A, may also be used, as will be appreciated by those of ordinary skillin the art. The crystal 170 can provide a precision time reference thatperforms a similar function as that of the clock channel 121 describedwith respect to FIG. 1A. Other arrangements for carrying statusinformation, including those described above with respect to FIG. 1A,may also be used, as will be appreciated by those of ordinary skill inthe art. FIG. 1B also illustrates the use of a resistor divider circuit160 to generate the specific voltage required to assign the memorymodule 150 a desired address. Therefore, it will be appreciated that theremainder of the specification is discussed with respect to theembodiment described in FIG. 1A, that alternative embodiments in whichmemory modules are implemented with one or more ICs are also within thescope of the invention described herein

FIG. 1C shows another electrical interface 171 according to anillustrative embodiment of the present invention. The interface 171includes a controlling computer system 172 in communication with aplurality of non-volatile memory modules 173 a, 173 b, . . . 173 x,which implement the basic functions as the embodiments described withrespect to FIGS. 1A and 1B. It will be appreciated that in theembodiments shown in FIGS. 1A and 1B, support for a common timereference is implemented either by a clock channel 121 or by a crystalcircuit 170, which can increase the number of connections between thecontrolling computer system 101 and the memory modules 103 a, 103 b, . .. 103 x or the incorporation of additional components into the memorymodules 103 a, 103 b, . . . 103 x, respectively. The electricalinterface 171 illustrated in FIG. 1C encodes a binary clock with values0 and 1, binary data transmission values of 0 and 1 along with busystatus and error status information on two open drain, three-levelchannels. These channels are the Address-Data/Error channel 178 and theClock/Busy channel 180.

When the Address-Data/Error 178 channel is at a low voltage it encodes alogical 0 data transmission state independent of whether any of thememory modules 173 a, 173 b, . . . 173 x, are reporting an errorcondition. When the Address-Data/Error 178 is at an intermediate voltagelevel it encodes a logical 1 data transmission state and that at leastone of the memory modules 173 a, 173 b, . . . 173 x is reporting anerror condition. When the Address-Data/Error 178 is at a high voltagelevel it encodes a logical 1 data transmission state and that none ofthe memory modules 173 a, 173 b, . . . 173 x are reporting an errorstate. The clamping of the maximum voltage to the intermediate level, asopposed to the high voltage determined by the pull-up resistor andcapacitor combinations 182 alone, can be achieved by the memory modules173 a, 173 b, . . . 173 x reporting an error state shorting theAddress-Data/Error 178 to ground through a zener diode or similarcomponent known in the art to limit the maximum voltage. When theClock/Busy channel 180 is at a low voltage it encodes a logical 0 clockstate independent of whether any of the memory modules 173 a, 173 b, . .. 173 x, are reporting a busy condition. When the Clock/Busy channel 180is at an intermediate voltage level it encodes a logical 1 clock stateand that at least one of the memory modules 173 a, 173 b, . . . 173 x isreporting a busy condition. When the Clock/Busy channel 180 is at a highvoltage level it encodes a logical 1 clock state and that none of thememory modules 173 a, 173 b, . . . 173 x are reporting a busy state. Theclamping of the maximum voltage to the intermediate level, as opposed tothe high voltage determined by the pull-up resistor and capacitorcombinations 182 alone, is achieved by the at least one of the memorymodules 173 a, 173 b, . . . 173 x reporting the busy condition shortingthe Clock/Busy channel 180 to ground through a zener diode or similarcomponent so as to limit the maximum voltage.

II. Addressing Memory Modules

In order for a processing device to send commands and receive responsesfrom a set of non-volatile memory modules distributed throughout aprinting or imaging device, each of the memory modules are firstassigned a memory module address according to an addressing scheme.Referring again to FIG. 1A, according to one aspect of the addressingscheme, the processing device 101 is capable of specifying a singlememory module and an address or addresses location within the memorymodule that is to be read or modified. According to another aspect ofthe addressing scheme, an individual, multiple, or all of the memorymodules may be issued the same command at the same time (e.g., a“broadcast” scheme). This allows a plurality of memory modules to beupdated in parallel.

In accordance with another embodiment of the present invention, thecommands described herein may also be issued to the memory modules 103a, 103 b, . . . 103 x using a split transaction scheme. The splittransaction scheme may achieve nearly the same overall level of parallelprocessing as the broadcast scheme if the time to transmit commands andresponses between the processing device 101 and the memory modules 103a, 103 b, . . . 103 x is relatively short when compared to the timeactually needed to process and accomplish the task specified by thecommand. The time needed to accomplish the task specified by the commandmight be relatively long, for example, due to the time needed to changeor replace the non-volatile memory contents of the memory modules 103 a,103 b, . . . 103 x or perhaps perform an intensive computation such as acryptographic (e.g., encryption and/or decryption) operation asdescribed in further detail below. Other commands that may require arelatively-long processing time include addressing commands, incrementcounter commands, punch out bit field commands, and other writing and/orcomputationally-intensive commands.

In a preferred embodiment, a split transaction scheme may be implementedwhere the memory modules 103 a, 103 b, . . . 103 x are operable to splitthe following operations into separate parts: 1) receive and verify thecommand to be free of transmission errors, 2) process the command (alsoreferred to as “processing the commanded task”), and 3) report the finaloutcome of the command to the processing device 101. In this splittransaction scheme, command-level synchronization using the statusconditions (e.g., busy, error, etc.) described above can be used todetermine whether a command has been received and/or processed by theaddressed memory module 103 a, 103 b, . . . 103 x.

In an exemplary embodiment of the split transaction scheme, assumingthat the memory modules 103 a, 103 b, . . . 103 x are ready, theprocessing device 101 can first issue a command to memory module 103 aand then await for this memory device 103 a to indicate the command wasreceived without error. After a relatively-short amount of time, thememory device 103 a can indicate to the processing device 101 that thecommand was received successfully by removing its busy status withoutindicating an error status. The memory device 103 a may begin processingthe command, which requires a relatively-lengthy operation time. Theprocessing device 101 can then proceed to issue the same or similarcommand to the memory module 103 b, where this transmission overlaps thelengthy processing time for memory module 103 a. This overlapping ofrelatively-short command transmissions with relatively-lengthyprocessing times for the command can be repeated as desired. Aftertransmitting and confirming the reception of the commands to all thememory modules 103 a, 103 b, . . . 103 x as desired, the processingdevice 101 can poll the memory modules 103 a, 103 b, . . . 103 x forindications that each has completed processing the command and is readyto accept another command.

FIGS. 8A and 8B illustrate exemplary time-flow diagrams for broadcastand split transaction schemes, respectively. In both 8A and 8B, thecommand transmission time, including checking for command transmissionerrors, is relatively short while the command processing time isrelatively long. For example, the command processing time may besubstantially larger than the command transmission time, perhaps, aboutthree to fifteen times greater than the command transmission timeaccording to an exemplary embodiment. One of ordinary skill in the artwill recognize that the ratio of the command processing time to thecommand transmission time may increase as the number of memory modulesto be utilized with the split transaction scheme increases. Theexemplary broadcast and split transaction schemes of FIGS. 8A and 8Bwill now be discussed below.

With respect to the broadcast scheme of FIG. 8A, the processing device101 broadcasts a command to each of the memory modules 103 a, b, c, d(block 802). Having received the command, each of the memory blocks 103a, b, c, d concurrently processes and completes the commanded task inthe time illustrated by blocks 804, 806, 808, and 810, respectively. Incomparison to the split transaction scheme of FIG. 8B described below,the amount of time gained 811 by the broadcast scheme of FIG. 8A can besmall if, as here, the ratio of the command transmission time to thecommand processing time is small.

FIG. 8B illustrates a split transaction scheme that achieves nearly thesame overall level of parallel processing as the broadcast scheme ofFIG. 8A. In FIG. 8B, the processing device 101 may first determine, viaone of the methods described herein, whether the memory modules 103 a,b, c, d are ready to receive data. As illustrated in FIG. 8B, if thememory modules 103 a, b, c, d are ready to receive data, the processingdevice 101 first transmits the command to the memory module 103 a, andchecks to ensure that the memory module 103 a received the commandwithout error (block 812). Once the processing device 101 confirms thatthe memory module 103 a received the command without error, perhaps viaa status condition, signal, or other indication on a channel asdescribed herein, the processing device 101 then transmits a command tothe memory module 103 b (block 816) while the memory module 103 aprocesses the commanded task (block 814).

Again, once the processing device 101 confirms that the memory module103 b received the command without error, the processing device 101transmits a command to the memory module 103 c (block S20) while thememory module 103 b processes the commanded task (block 818). Similarly,once the processing device 101 confirms that the memory module 103 creceived the command without error, the processing device 101 transmitsa command to the memory module 103 d (block S20) while the memory module103 c processes the commanded task (block 818). The memory module 103dthen processes the commanded task. When each of the memory modules 103a, b, c, d completes the commanded task, a status condition (e.g.,ready, error) may be provided or updated for the processing device 101.One of ordinary skill will readily recognize that while four exemplarymemory modules are described in FIGS. 8A and 8B, other embodiments mayutilize fewer or more memory modules without departing from the presentinvention.

The split transaction scheme as illustrated in FIG. 8B may, in someinstances, be easier to manage in comparison to the broadcast scheme ofFIG. 8A because the error-free transmission of a command to each memorymodule is confirmed before the transmission of a command to the nextmemory module. By contrast, in the broadcast scheme illustrated in FIG.8A, some memory modules may receive the command correctly and performthe commanded task, while other memory modules may not receive thecommand properly and would not be able to perform the task. Accordingly,error recovery from this broadcast scheme of FIG. 8A may be more complexthan in the split transaction scheme of FIG. 8B to achieve the desiredparallel processing. Further, if message authentication codes are usedto insure that only commands received from authorized sources areexecuted, the use of the split transaction method may avoid the use of asingle “initialization vector” value supplied to the memory modules 103a, 103 b, . . . 103 x from the processing device 101 for all broadcastcommands. Because commands are transmitted to one memory module at atime in the split transaction scheme, the “initialization vector” usedfor each transmission operation provided to the processing device 101 byeach memory module 103 a, 103 b, . . . 103 x can be unique. One ofordinary skill in the art will readily recognize many variations of thesplit transaction scheme described above. For example, instead ofcommanding individual memory modules sequentially as described above, afirst set of memory modules may be commanded followed by a second set ofmemory modules. In addition, in another alternative embodiment, thecommands utilized with the respective memory modules in the broadcastscheme may not be the same commands, but rather one or more commandsthat are processed in a similar amount of time.

Returning back to the addressing of the memory modules, a variety ofmethods are possible for an addressing scheme. According to oneembodiment, a singular addressing scheme may be applied to the memorymodules. With a singular addressing scheme, a specified number of bitsin a communications protocol are allocated for the “memory moduleaddress.” As necessary, each of the bits (or at least a portion thereof)in the memory module address corresponds to a particular memory module.For example, as shown in FIG. 2A, if eight bits are allocated for thememory module address, and there are eight memory modules 103 a, 103 b,. . . 103 h, each memory module may be assigned to one of the eight bitsin the memory module address 200. Each of the memory modules 103 a, 103b, . . . 103 h will understand that it is being addressed when itscorresponding bit in the memory module address 200 is at a specificstate (e.g., high or a “1”). By setting a plurality of bits in thememory module address 200, the corresponding plurality of memory modulesmay be addressed simultaneously by the processing device 101. Forinstance, if memory modules 103 c, 103 d, and 103 g are to be addressedat the same time, then the illustrative memory module address 202 shownin FIG. 2B may be utilized. Alternatively, if the split transactionscheme described above and illustrated in FIG. 8B is implemented, abinary-coded address or other unique memory module address can be usedwhere any one command addresses only a single memory module usingsingular addressing.

A method by which memory modules are assigned an address under thesingular addressing scheme will now be described in more detail. Manyvariations of address assignments are possible with commands or softwareactivity. However, it is also possible to assign an address to a memorymodule without the use of issued commands or software. One embodiment isshown in FIG. 1A, in which a conductor 114 with a set of discretevoltage levels is provided through the use of resistors 118, and whereeach discrete voltage level corresponds to a particular bit position inthe memory module address. Each of the plurality of memory modules 103a, 103 b, . . . 103 x will be in communication with the conductor 114,and will be assigned a memory module address based on the discretevoltage level of the conductor 114. For example, the discrete voltagesof 3.3V may be provided for memory module 103 a while a discrete voltageof 3.0V may be provided for memory module 103 b. In this example, memorymodule 103 a may be assigned the first bit position in the memory moduleaddress and memory module 103 b may be assigned to the next bit positionadjacent to the first bit position. The use of a single conductor 114 toassign addresses also reduces the number of connections required forimplementing the addressing scheme, and simplifies the connectionsneeded for memory modules packaged on removable components such as printcartridges.

According to an alternative embodiment, separate conductors, each with adiscrete voltage, could be utilized with each of the memory modules 103a, 103 b, . . . 103 x. In yet another alternative embodiment, thespecific address of a memory module may be assigned by a resistordivider circuit designed to produce a specific voltage level based uponthe specific component of the imaging device. This would allow thereduction of another connection between the processing device 101 andthe memory modules 103 a, 103 b, . . . 103 x. In addition, according toanother alternative embodiment, the address/data channel 108 could beutilized to program an address for each of the memory modules 103 a, 103b, . . . 103 x. According to yet another alternative embodiment of thepresent invention, the addresses of each of the memory modules 103 a,103 b, . . . 103 x may be pre-defined prior to its inclusion within theelectrical interface 100.

Further, within each memory module 103 a, 103 b, . . . 103 x, theaddresses or locations that are to be read or modified may be assigned.According to one embodiment, the processing device 101 may assign theaddress or location by using a hardware strapping capability. As anexample, the processing device 101 may provide that particular counts ineach memory module 103 a, 103 b, . . . 103 x will be assigned to aparticular address or location. For example, within each memory module103 a, 103 b, . . . 103 x, a total page count may be assigned to oneaddress, a number of printed color pages to a second address, a numberof printed monochrome pages to a third address, a number of letter-sizedprinted pages to a fourth address, a number of legal-sized printed pagesto a fifth address, and a number of printed transparencies to a sixthaddress, and so on. Further, the address or location in a memory module103 a, 103 b, . . . 103 x may be specified for resource usage bit fieldsthat may be utilized in metering resource usage in print cartridges.

III. Command Protocols

The command sets and protocols (also referred to as “command protocols”)utilized in accordance with an embodiment of the present inventionsupport the writing of data to and the reading of data from one or morememory modules 103 a, 103 b, . . . 103 x. FIG. 3 is a block diagram flowchart of an exemplary write data command protocol that allows aspecified value to be written to one or more locations in one or morememory modules 103 a, 103 b, . . . 103 x. As shown in FIG. 3, the writedata command protocol 300 includes sets of bits representing the writedata command 302, the memory module address 304, the length of the listof locations 306, the corresponding locations 308, and the data to bewritten 310. The write data command 302 may be, for instance, an eightbit field representing the “write data” command. The memory moduleaddress 304 may be, for instance, a sixteen bit field utilizing singularaddressing to indicate which of the potential sixteen memory modules 103a, 103 b, . . . 103x the command 302 is addressed to. As indicated abovewith singular addressing, one memory module, a set of memory modules, orall of the memory modules 103a, 103b, . . . 103x may be addressedsimultaneously by setting each of the respective bits in the memorymodule address to a “1 ”. The length of the locations 306, perhaps aneight bit field, may indicate how many locations within each memorymodule 103 a, 103 b, . . . 103 x are to be updated. Each of the locationnumbers 308 may be for instance, a sixteen bit field indicating theaddress of the location in the memory module 103 a, 103 b, . . . 103 xthat is to be updated. As an example, if four separate locations are tobe updated, then the length of the list of locations 306 will be four,and there may be four separate sixteen-bit location numbers 308specified. The data to be written 310 represents the specified data thatis to be written in each of the locations 306.

Once the write data command protocol 300 is prepared, it is transmittedto each of the memory modules 103 a, 103 b, . . . 103 x (blocks 312,314) if the memory modules are all ready (e.g., status signal 110 at ahigh voltage level). If the memory module address 304 indicates that aparticular memory module 103 a, 103 b, . . . 103 x is being addressed,then each memory module 103 a, 103 b, . . . 103 x that is beingaddressed pulls its status signal 110 to a low voltage to indicate abusy status (block 316) while it processes the write data command 302(block 318). If the memory module 103 a, 103 b, . . . 103 x encountersan error while processing the write data command 302 (block 320), itsstatus signal 110 may be placed at an intermediate voltage level toindicate an error (block 322). Assuming no error is encountered, eachaddressed memory module 103 a, 103 b, . . . 103 x will write the datavalue 310 to each of the locations 306. When the write data command 302is completed (block 324), the memory module 103 a, 103 b, . . . 103 xreleases its status signal from a low voltage level to a high voltagelevel to signify completion of the command 302 (block 326).

In addition to the writing of specified data values to particularlocations, command protocols are also supported in order to have one ormore counters incremented. According to one embodiment of the invention,another command protocol of the present invention is an incrementcounter command protocol, which permits the memory modules to receive anincrement counter command. With an increment counter command, eachmemory module may include a counter that maintains its own count, whichis increased by a specified value upon receipt of the increment countercommand. The increment counter command may be utilized with a pluralityof counters with different counts—for example global page counts, colorpage counts, letter-sized page counts, legal-sized paged counts,transparency page counts, etc. Thus, the global page count, the colorpage count, the letter-sized page counts, and the transparency pagecounts in one or more memory modules 103 a, 103 b, . . . 103 x may beincremented at the same time, which makes it unnecessary for theprocessing device 101 to know of the present values of each of thosecounts that are being updated. Instead, each memory module 103 a, 103 b,. . . 103 x is responsible for maintaining its own counts and updatingthe counts upon receipt of the increment counter command protocol.

As shown in FIG. 4A, similar to the write data command protocol 300, theincrement counter protocol 400 includes a set of bits allocated for theincrement counter command 402, the memory module address 404, the valuethat each counter will increment by 406, the length of the list ofcounters 408, and the address of each counter to increment within thememory module 410. According to one illustrative example, the incrementcounter command 402 may be eight bits, the memory module address 404 maybe sixteen bits, the value that each counter will increment by 406 maybe eight bits, the length of the list of counters 408 may be eight bits,and the address of each counter 410 may be sixteen bits. Each memorymodule 103 a, 103 b, . . . 103 x that is addressed will pull the signalon the status channel 110 to a low voltage to signify that it is busywhile it updates one or more counters by the value specified. The memorymodule 103 a, 103 b, . . . 103 x will release the signal on the statuschannel 110 to a high voltage to signify that it is ready after eachaddressed counter has been updated.

Referring next to FIG. 4B, the protocol 420 for commands to punch out aresource bit field is shown, according to one embodiment of theinvention. The punch out protocol 420 includes a plurality of bitsallocated for the punch out bit field command 422, the memory moduleaddress 424, the length of list of bit-field numbers to address 426, andthe address of each bit field number in the memory module 428. Accordingto one illustrative embodiment, the punch out bit field command 422 maybe eight bits, the memory module address 424 may be sixteen bits, thelength of the list of bit-field numbers 426 may be eight bits, and theaddress of each bit field number 428 may be sixteen bits. No data valueneeds to be specified because the punch out bit field command 422 doesnot require that a memory module 103 a, 103 b, . . . 103 x updates aparticular value, but only to punch out a particular bit field (e.g.,changed from an erased state to a programmed state).

FIG. 5 is block diagram flow chart of an exemplary read data commandprotocol that allows the processing device 101 to query a particularmemory module 103 a, 103 b, . . . 103 x for a stored value. The readdata command protocol 500 differs from the write command protocols abovein that the addressed memory module 103 a, 103 b, . . . 103 x sends data522 back to the processing device 101. Referring to FIG. 5, the readdata command protocol 500 includes sets of bits representing the readdata command 502, the memory module address 504, the length of the listof locations 506, and the corresponding locations 508. For example, thecommand 502 may consist of an eight bit long command representing the“read” data command for a memory module 103 a, 103 b, . . . 103 x. Thememory module address 504 may be a sixteen bit field utilizing singularaddressing to indicate which of the potential sixteen memory modules 103a, 103 b, . . . 103 x the command is addressed to. The length of thelist of locations 506, perhaps an eight bit field, will indicate howmany locations within each memory module 103 a, 103 b, . . . 103 x areto be read. Each of the location numbers 508 may be perhaps a sixteenbit field indicating the address of the location in the memory module103 a, 103 b, . . . 103 x that is to be read.

Once the read data command protocol 500 is prepared, it is transmittedto each of the memory modules 103 a, 103 b, . . . 103 x (blocks 510 and512) assuming that the memory modules 103 a, 103 b, . . . 103 x areready (e.g., the status signal 110 is at a high voltage). If the memorymodule address 504 indicates that a particular memory module 103 a, 103b, . . . 103 x is being addressed, then the memory module 103 a, 103 b,. . . 103 x that is being addressed pulls its status signal 110 to a lowvoltage to signify a busy status (block 514) while it processes the readdata command 502 (block 516). If the memory module 103 a, 103 b, . . .103 x encounters an error while processing the read data command 502,then its status signal 110 may be pulled to an intermediate voltagelevel to signify an error status (block 520). Assuming no error isencountered, data 522 retrieved from the requested location numbers willbe sent to the processing device 101. Once the write command has beencompleted (block 524), the memory module releases its signal on thestatus channel 110 from a low voltage level to a high voltage level(block 526).

Because the memory modules 103 a, 103 b, . . . 103 x may sometimesreport errors by holding the status channel 110 at an intermediatevoltage level, a command protocol to read the status of the memorymodules is needed. When the processing device 101 detects that an errorhas occurred, it may individually query each of the memory modules 103a, 103 b, . . . 103 x with a “read status” command 642. As illustratedin FIG. 6A, this protocol 640 may include a set of bits representing theread status command 642 and the memory module address 644. The readstatus command 642 may be, for instance, eight bits and the memorymodule address 644 may be sixteen bits. After processing the read statuscommand 642, the addressed memory module 103 a, 103 b, . . . 103 x maythen respond with its current status and return its status channel 110to the Ready status (e.g., a high voltage level).

One error that a memory module 103 a, 103 b, . . . 103 x may report isthat one of its counters is not maintaining a value as expected. Thismay occur because particular locations in the non-volatile memorymodules 103 a, 103 b, . . . 103 x may degrade over time with use. Insuch a situation, the processing device 101 may send a command to setthe next available location. As shown in FIG. 6B, this protocol 660 mayinclude a set of bits representing the set next available locationcommand 662, the memory module address 664, and the address of the nextavailable location 666. According to an illustrative example, the setnext available location 662 may be eight bits, the memory module address664 may be sixteen bits, and the address of the next available location666 may be sixteen bits. In an alternative embodiment of the presentinvention, the set next available location command protocol 660 may notbe necessary if each memory module 103 a, 103 b, . . . 103 x is able toautomatically remap a counter or bit field to a new address or locationwithout assistance from the processing device 101. According to yetanother alternative embodiment of the present invention, one or morereserved memory modules may be provided such that a faulty memory modulemay be remapped to one of the reserved memory modules, eitherautomatically or with assistance from the processing device 101.

One of ordinary skill will recognize that many variations and additionsto the described command protocols are possible. For example, adifferent number of bits may be used for the memory module addresses andfor the address/locations in the command protocols. For example, eightbits or twenty-four bits may be used for the memory module address aswell to accommodate fewer or more memory modules 103 a, 103 b, . . . 103x. In addition, the fields contained in each of the command protocolsmay be rearranged in other orders as well. For example, in the writedata command protocol 300, the data that is to be written 310 could beplaced between the memory module address 304 and the length of thelocations 306. In addition, horizontal parity bits, vertical paritybits, or both may be used with the transmitted protocols for checkingand resolving transmission errors. Further, for security purposes,authentication may be utilized between the memory modules 103 a, 103 b,. . . 103 x and processing device 101. For example, in FIG. 3, the data310 may be encrypted prior its transmission to the memory modules 103 a,103 b, . . . 103 x. In such a case, the memory module will beresponsible for decrypting the data 310. A variety of encryptionalgorithms known in the art may be utilized, including an RSA encryptionalgorithm (e.g., 1024-bit, 2048-bit, etc.) that utilizes asymmetricalkeys (e.g., public and private keys). If encryption/decryption isutilized, then the command protocols may also support reading asymmetrickeys and accepting asymmetric keys from the processing device 101 andmemory modules 103 a, 103 b, . . . 103 x. In addition, the memorymodules 103 a, 103 b, . . . 103 x, including those provided with printcartridges, may include serial numbers to authenticate the manufacturerof the cartridges. Accordingly, a command protocol may be supported inorder to read the serial number from the memory module. The read serialnumber command protocol may include a set of bits for the read serialnumber command and the memory module address. A memory module 103 a, 103b, . . . 103 x that receives the read serial number command protocolwill respond with its serial number.

FIG. 7 shows a block diagram flow chart illustrating a method ofcommunicating with one or more memory modules, such as one or morenon-volatile memory modules, according to one embodiment of the presentinvention. As shown in FIG. 7, the method may begin with a processingdevice, such as the illustrative processing device 101 of FIG. 1A,receiving a status signal from one or more memory modules (block 702)instructing the processing device that the one or more memory modulesare prepared to receive data. According to one embodiment of theinvention, the one or more memory modules may be one or more of thememory modules 103 a, 103 b, . . . 103 x illustrated in FIG. 1A. Thestatus signal may be an ‘available’ status signal, as described indetail above. Next, the processing device generates a packet including acommand and one or more memory module addresses (block 704) to which thecommand will be transmitted. According to one aspect of the invention,the command is an increment counter command to increment one or more ofthe memory modules by an increment value also included in the command.According to other aspects of the invention, the command may include apunch out bit field command, and/or a write data command, both of whichwere described above. Referring again to FIG. 7, after the processingdevice transmits the packet to the one or more memory modules (block706), the one or more memory modules process the received packet andtransmit a ‘busy’ status signal to the processing device whileprocessing the packet (block 708). After the one or more memory modulescomplete processing the packet (block 710), an available status signalmay be sent to the processing device, which receives the status (block702) so that additional commands may be sent to the one or more memorymodules.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. A method of updating a memory module,comprising: receiving, at a memory module, a command indicative of usageof toner or ink in a consumable item for an imaging device forinstructing the memory module to punch out at least one bit of at leastone specified bit field within the memory module indicative of the usageof toner or ink; and processing the command at the memory module.
 2. Themethod of claim 1, wherein the processing of the command compriseschanging the at least one bit from an erased state to a programmedstate.
 3. The method of claim 1, wherein the at least one bit comprisesa plurality of bits and the at least one specified bit field comprises aplurality of separately specified bit fields such that each bitcorresponds to a distinct specified bit field.
 4. The method of claim 3,wherein the plurality of bits comprises at least eight bits.
 5. Themethod of claim 1, further comprising receiving a second command,wherein the second command is operable to instruct the memory module toincrement a non-volatile counter therein.
 6. The method of claim 5,wherein the processing comprises incrementing the counter by an amountspecified in the command.
 7. The method of claim 5, wherein theprocessing comprises processing the command and the second command,including at least one of changing the at least one bit from an erasedstate to a programmed state and incrementing the counter.
 8. The methodof claim 7, wherein incrementing the counter comprises incrementing thecounter by an amount specified in the command.
 9. The method of claim 1,wherein the processing comprises: upon encountering an error conditionwhile processing the command, limiting voltages on a first interfacesignal line of the memory module to be no more than an intermediatevoltage greater than voltage levels corresponding to a binary zero stateand less than voltage levels corresponding to a binary one state.
 10. Amemory module, comprising: a plurality of memory bits, wherein thememory module receives at least one command indicative of usage of toneror ink in a consumable item for an imaging device and instructs thememory module to punch out at least one bit in at least one specifiedbit field within the memory module indicative of the usage of toner orink, and processes the at least one command.
 11. The memory module ofclaim 10, wherein the memory module processes the at least one commandby changing the at least one bit in the at least one specified bit fieldfrom an erased state to a programmed state.
 12. The memory module ofclaim 10, wherein the at least one bit comprises a plurality of bits andthe at least one specified bit field comprises a plurality of separatelyspecified bit fields, each bit corresponding to a distinct bit field.13. The memory module of claim 10, wherein the memory module includes anon-volatile counter and the at least one command includes a secondcommand for instructing the memory module to increment the non-volatilecounter therein.
 14. The memory module of claim 13, wherein the memorymodule processes the at least one command by changing the at least onebit in the at least one specified bit field from an erased state to aprogrammed state and incrementing the non-volatile counter.
 15. Thememory module of claim 14, wherein the memory module processes the atleast one command by incrementing the non-volatile counter by an amountspecified in the at least one command.
 16. The memory module of claim10, wherein the memory module includes a first interface signal line forcommunicating with a processing device, the memory module processes theat least one command by: upon encountering an error condition whileprocessing the at least one command, limiting voltages on the firstinterface signal line to be no more than an intermediate voltage greaterthan voltage levels corresponding to a binary zero state and less thanvoltage levels corresponding to a binary one state for a period of timeto indicate an occurrence of the error condition.
 17. A memory module,comprising: a plurality of memory cells; and a plurality of signal linesfor communicating with a processing device, the memory module configuredsuch that following reception of a command and upon encountering anerror condition while processing the command, limiting a voltage on afirst signal line of the plurality of signal lines to be no more than anintermediate voltage greater than voltage levels corresponding to abinary zero state and less than voltage levels corresponding to a binaryone state for a period of time to indicate an occurrence of the errorcondition; wherein the command is indicative of usage of toner or ink ina consumable item for an imaging device and instructs the memory moduleto punch out at least one memory cell in at least one specified bitfield within the memory module indicative of the usage of toner or ink,following reception of the command, the memory module processes the atleast one command.
 18. The memory module of claim 17, wherein the memorymodule processes the command by changing the at least one cell from anerased state to a programmed state.
 19. The memory module of claim 17,further comprising at least one resistor coupled between the firstsignal line and a ground potential, the memory module causing current topass through the at least one resistor for limiting a voltage on thefirst signal line to be no more than the intermediate voltage.
 20. Thememory module of claim 19, wherein the intermediate voltage is based atleast in part upon a resistance of the at least one resistor.
 21. Thememory module of claim 17, further comprising at least one diode coupledbetween the first signal line and a ground potential, the memory modulecausing current to pass through the at least one diode for limiting avoltage on the first signal line to be no more than the intermediatevoltage.
 22. The memory module of claim 17, further comprising at leastone electrical component coupled between the first signal line and aground potential, the memory module causing current to pass through theat least one electrical component for limiting a voltage on the firstsignal line to be no more than the intermediate voltage.
 23. The memorymodule of claim 17, wherein the plurality of signal lines includes asecond signal line, and wherein following reception of the command, thememory module limits a voltage on the second signal line to be nogreater than a second intermediate voltage between the voltagescorresponding to the logic zero state and the voltages corresponding tothe logic one state for a period of time to indicate a busy condition.24. The memory module of claim 23, wherein the second intermediatevoltage is substantially the same as the first intermediate voltage. 25.The memory module of claim 23, wherein the memory module receives on thesecond signal line a second input signal.
 26. The memory module of claim25, wherein the second input signal comprises a clock input signal. 27.The memory module of claim 23, further comprising at least one resistorcoupled between the second signal line and a ground potential, thememory module causing current to pass through the at least one resistorfor limiting a voltage on the second signal line to be no more than thesecond intermediate voltage.
 28. The memory module of claim 23, furthercomprising at least one diode coupled between the second signal line anda ground potential, the memory module causing current to pass throughthe at least one diode for limiting a voltage on the second signal lineto be no more than the second intermediate voltage.
 29. The memorymodule of claim 23, further comprising at least one electrical componentcoupled between the second signal line and a ground potential, thememory module causing current to pass through the at least oneelectrical component for limiting the voltage on the second signal lineto be no more than the second intermediate voltage.
 30. A memory module,comprising: memory cells for storing information therein; and aplurality of signal lines for communicating with a processing device,the memory module configured such that following reception of a commandon the signal lines and during processing thereof, a voltage on a firstsignal line of the plurality of signal lines is limited for a period oftime by the memory module to be no more than an intermediate voltagegreater than voltages corresponding to a binary zero value and less thanvoltages corresponding to a binary one value, for indicating by thememory module one of a busy condition and an error condition; whereinthe command pertains to usage of toner or ink in a consumable item foran imaging device for instructing the memory module to punch out atleast one bit of at least one specified bit field within the memorymodule to indicate the usage of toner or ink, and wherein the memorymodule processes the command following the reception thereof.
 31. Thememory module of claim 30, wherein the memory module receives on thefirst signal line a first input signal.
 32. The memory module of claim30, further comprising at least one electrical component coupled betweenthe first signal line and a ground potential such that the memory modulepasses current through the at least one electrical component forlimiting the voltage on the first signal line to be no more than theintermediate voltage.
 33. The memory module of claim 32, wherein theintermediate voltage is based at least in part upon a resistancecorresponding to the at least one electrical component.
 34. The memorymodule of claim 30, further comprising at least one diode coupledbetween the first signal line and a ground potential such that thememory module passes current through the at least one diode for limitingthe voltage on the first signal line to be no more than the intermediatevoltage.
 35. The memory module of claim 30, wherein the plurality ofsignal lines includes a second signal line, and wherein the memorymodule is configured such that following reception of the command andduring processing thereof, a voltage on the second signal line islimited for a second period of time by the memory module to be no morethan a second intermediate voltage greater than the voltagescorresponding to the binary zero value and less than the voltagescorresponding to the binary one value, for indicating one of the busycondition and the error condition not indicated on the first signalline.
 36. The memory module of claim 35, wherein the second intermediatevoltage is substantially the same as the first intermediate voltage. 37.The memory module of claim 30, wherein the at least one bit comprises asingle bit.